The Premier League and the English Football Association will begin trial periods for concussion substitutes at the start of February.
The International Football Association Board (The IFAB) confirmed last month that global trials would run through to March 2022. Permanent substitutions will be introduced into the Premier League as of Matchweek 23 on Feb. 6, the same date the FA will also introduce them into the Women's Super League; they will be used in the FA Cup as of the fifth round on Feb. 9.
Protocols will allow a maximum of two concussion substitutes to be used per team; if one team makes an enforced change the opposition will be granted an addition substitution. The concussion subs may be made regardless of the number of substitutions a team has made already.
An alternative, which may be trialled in other competitions globally, gives only one concussion substitute per team, but the opposition would not be allowed to make another change too.
"Whilst two suspected concussions on one team are incredibly unlikely, it is nonetheless a possibility," FA CEO Mark Bullingham told ESPN in December. "So we think having an option where that's possible is better. There are pros and cons of both models but the advantage of the model where you can have substitutes coming on for the other team, we think is fairer.
"We don't think that the team should gain advantage from someone going off with a suspected concussion. We think that actually the other team having a substitute is fairer."
The trials come after extensive discussions by The IFAB's Concussion Expert Group, which consists of medical concussion experts, team doctors, player representatives and coaches, agreed upon an "if in doubt, take them out" philosophy. Players will be assessed and if there is any question about their ability to continue in the game they will be replaced.
The Premier League and the FA Cup now allow nine substitutes to be named for each game to cover the possible increase in changes. If both teams use two concussion subs, technically there could be seven subs a team in the Premier League and nine in the FA Cup.
FIFpro, the players' union, had wanted the IFAB to bring in temporary substitutes for a 10-minute assessment period but it was decided that player welfare issues meant permanent substitutes would be safer.